Sample applicator

ABSTRACT

An applicator for applying aqueous test solutions to a hydrated gel layer for subjection to electrophoretic or chromatographic procedures is in the form of a stiff resilient non-absorbent polymeric sheet having a thickness from 3 to 125 mils and having a hydrophilic surface. The thin film of test solution picked up by the sample holder when dipped in the solution is transferred with precise control of location by pressing the edge of the applicator into the gel.

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Forget et al. Dec. 24, 1974 SAMPLE APPLIQATOR 3,358,496 12/1967 Farmer73/61.1 c 3,470,847 10/1969 Chapin et al. ll8/506 X [75] Invenmrs-Rmlald f Owl Head 3,495,446 2/1970 Williamson 73/6l.l c 3 m' Waban,3,505,858 4/1970 Kohn 73 61-.1 c

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[73] Assignee: Marine Colloids, lnc., Rockland, primary Examiner l)onaldO Woodie] Mame Assistant Examiner-Joseph W. Roskos [22] Filed: Apr. 7,1972 [21] Appl. No.: 241,921 57 ABSTRACT An applicator for applyingaqueous test solutions to a [52] Cl 6 C.15/236 0 4 hydrated gel layerfor subjection to electrophoretic or [51] Int Cl G01 31/08chromatographic procedures is in the form of a stiff [58] Fi i Cresilient non-absorbent polymeric sheet having a e 2 53: S j thicknessfrom 3 to 125 mils and having a hydrophilic 210/31 C 0 15/256 117/111 fsurface. The thin film of test solution picked up by the 118/506. 401/46 264 sample holder when dipped in the solution is transp 4 ferred withprecise control of location by pressing the 5 6] References Cited edgeof the applicator into the gel.

UN TED STATES PATENTS 5 Claims, 6 Drawing Figures 2,868,020 l/l959Williams, J1. 73/61.] C 'X PATENTED UEB-24IBH FLT! I n l8 IFIG. 3

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SAWLE APPLICATOR This invention relates to an applicator for applyingaqueous test samples to hydrated gel films for subjection toelectrophoretic or chromatographic procedures.

In carrying out such procedures it is important, for best results, toplace a small controlled quantity of the aqueous test solution in aprecisely controlled location in or on the gel film. In the past it hasbeen customary to use applicators consisting of a pair of parallel wiresholding the sample of test solution between them by capillary attractionor other forms of .devices relying on capillarity for holding anddelivering the sample. These devices do not provide close control overthe sample, and they make it difficult to locate the sample in asprecisely defined a location as desired. In addition,they require thedevelopment of considerable manual skill for effective use.

The present invention provides a sample applicator simple andinexpensive in construction and simple in operation, requiring little orno skill for-successful use. In the drawings:

FIG. I is an isometric view showing one embodiment of the presentinvention;

FIG. 2 is a sectional view taken along line 2-2 FIG. I;

' FIG. 3 is a view in side elevation showing the applicator of FIG. 1removably mounted upon a carrier;

FIG. 4 is a sectional view along line 44 of FIG. 3 showing a samplebeing applied to a gel film; FIG. 5 is a view inside elevation ofanother embodiment of the invention; and

FIG. 6 is a sectional view along line 6-6 of FIG. 5.

As shown in the drawings, the applicator of the pres- 'ent inventioncomprises a stiff, resilient sheet of synthetic polymeric materialhaving a plurality of projecting spaced apart sample holders l0, 10having nonporous non-absorbent hydrophilic surfaces upon which water andaqueous solutions readily spread to form thin films of relativelyunifonn thickness. Means for mount ing the sample holders on a handle isprovided in the form of a layer of pressure sensitive adhesive 12covered with a release paper 14 bonded to one face of the sheet alongthe length thereof near its upper edge.

In order to use the applicator the release paper 1 4 is removed and theapplicator is removably mounted on rigid plastic handle 16 by pressingthe adhesive surface against the surface of the handle. The sampleholders 10 are then dipped to any desired depth in the aqueous samplesolution, withdrawn together with a thin film of the, solution adheringto their wetted surfaces, and then pressed against the hydrated gellayer or film 18 to which. the sample is to be applied as shown'in FIG.4, preferably penetrating the gel, and withdrawn, leaving a deposit ofthe sample solution where the sample holders have come into contact withthe gel.

Sample holders 10 may-be of any convenient thickness from 3 to 125 mils,preferably 3 to 10 mils. I-Iolders much thinnerthan 3 mils tend to beunsatisfactory because of excessive flexibility or fragility whenpressed against the gel surface, while those thicker than 125 mils tendto deposit the sample over too large an area. The length of the bottomor gel-contacting edge of each sample holder, all of which arepreferably straight and aligned with each other, is a matter of choice,usually ranging from about one-fourth to l inch. The size of the spacesbetween sample holders is also a matter of choice, usually being of theorder of one-eighth to one-fourth inch. The height of each sample holderand handle measured in a direction perpendicular to the bottom orgelcontacting edge must be sufiiciently great so that the fingers of theoperator do not come into contact with the sample or with the gelsurface. It is desirable that the spacesbetween adjacent sample holders10 be 'sufiiciently deep so that their upper edges do not come intocontact with the gel whenthe samples are being applied, so that eachsample deposited by each sample holder is separate and distinct fromneighboring deposits, being spaced apart from them by the width of thespace between adjacent sample holders.

The polymeric sheet material from which the applicator is formed may beany one of a wide variety of syn-' thetic materials which are relativelystiff, resilient, and non-porous in nature such as polystyrene,polypropylene, polymethyl methacrylate, polyacrylic esters,superpolyamides such as nylon, polyesters such as polyethyleneterephthalate, polycarbonates, polyvinyl chloride, polyvinyl butyral,copolymers of acrylonitrile, butadiene, and styrene, and manyothers. Thesurface of the sheet forming the sample holders must be hydrophilic,i.e., capable of being readily wet by water and aqueous solutions sothat the latter spread into a thin film on the surface rather thanstanding in the form of beads or droplets of indeterminate size anddistribution. The foregoing polymeric materials are for the most parthydrophobic rather than hydrophilic in nature, so that the surface ofthe sheet must be subbed or treated by any oneof the numerous well knownprocedures for rendering it hydrophilic, among which are exposure to'anelectric corona discharge, treatment with ozone, ultraviolet radiation,concentrated sulfuric acid, tetraethyl titanate, tetraisopropyltitanate, nitrous oxide, copolymers of 'vinylidene chloride, acrylicester and itaconic acid, gelatin and others. Two or more of suchprocedures may be used in combination, either simultaneously orsuccessively, as is well known. In general, a surface against whichwater forms a contact angle from 0 to. 10 is sufficiently hydrophilicfor use in the present invention; preferably the contact angle is 0.

The hydrated gel films 18 commonly employed in chromatographic andelectrophoretic procedures, including such materials as agar, agarose,starch, polyacrylamide, and the like, are usually in the form of a filmor layer from 1 to 2 millimeters in thickness and are tender, readilycut materials supported, during the electrophoretic or chromatographicprocedure, upon a rigid support or backing member 20 (FIG. 4). In usingthe applicator, it is preferred to hold it at right angles to thesurface of the gel film, asshown in FIG. 4, and press it against therigidly supported film to penetrate and cut the latter substantiallythroughout its thickness by means of the straight bottom edges whiledepositing the sample solution.

The applicator of the present invention can also be used to deposit asample at the bottom of a slot or well, which has been precut orpreformed in the gel film.

Another form of the applicator of the present invention is shown inFIGS. 5 and 6 in which the stiff resilient sheet forming sample holders22, 22 is embedded in a handle 24 of plastic material, the entire devicebeing disposable.

Excellent results have been attained by using as the flexible sheet a 4mil sheet of polyethylene terephthalate subbed with a copolymer ofvinylidene chloride, acrylic ester and itaconic acid and with gelatincured by heating, sold under the trademark Cronar. With this material, asample holder one-fourth inch in width can be used to deposit a sampleas small as 0.5 microliter on a gel film. Excellent results have alsobeen obtained using polymethyl methacrylate for handle 16, whilepolyethylene is suitable for handle 24. The sheet from which sampleholders 22 are made may be simply a friction fit within a slot in handle24. While individual sample holders may be separately attached to thehandles, it is preferred, when more than a single sample holder is to beattached to an individual handle, to cut all of them from a single sheetof material, leaving them connected at their upper ends as appears inFIG. 1.

The capacity of the sample holders for holding aqueous solution can beincreased, if desired, by slightly abrading or roughening the surface,for example by scraping gently with a penknife.

What is claimed is:

1. An applicator for applying samples of aqueous test solution to ahydrated gel film for subjection to electrophoretic or chromatographicprocedures comprising a plurality of spaced apart stiff resilientnon-absorbent polymeric sheet sample holders having a thickness from 3to mils and having a hydrophilic surface each sample holder having anuninterrupted straight flat bottom.

2. An applicator as claimed in claim 1 comprising in addition means forremovably mounting said applicator upon a handle.

3. An applicator as claimed in claim 2 in which said means comprises alayer of pressure sensitive adhesive bonded to said sheet.

4. An applicator as claimed in claim 1 in which all of the sampleholders are integral parts of a single sheet and all have theirstraightedges aligned with each other for contacting said gel film.

5. An applicator for applying a sample of aqueous test solution to ahydrated gel film supported on a rigid support member for subjection toelectrophoretic or chromatographic procedures comprising a stiffresilient non-porous sheet of polymeric material having a thickness from3 to 10 mils and having a hydrophilic surface on which water spreads toa thin film, the bottom edge of said sheet being straight, flat, andfree from grooves and a handle connected to said sheet.

1. AN APPLICATOR FOR APPLYING SAMPLES OF AQUEOUS TEST SOLUTION TO AHYDEATED GEL FILM FOR SUBJECTION TO ELECTROPHORETIC OR CHROMATOGRAPHICPROCEDURES COMPRISING A PLURALITY OF SPACED APART STIFF RESILENTNON-ABSORBENT POLYMERIC SHEET SAPLE HOLDERS HAVING A THICKNESS FROM 3 TO125 MILS AND HAVING A HYDROPHILIC SURFACE EACH SAMPLE HOLDER HAVING ANUNINTERRUPTED STRAIGHT FLAT BOTTOM.
 2. An applicator as claimed in claim1 comprising in addition means for removably mounting said applicatorupon a handle.
 3. An applicator as claimed in claim 2 in which saidmeans comprises a layer of pressure sensitive adhesive bonded to saidsheet.
 4. An applicator as claimed in claim 1 in which all of the sampleholders are integral parts of a single sheet and all have their straightedges aligned with each other for contacting said gel film.
 5. Anapplicator for applying a sample of aqueous test solution to a hydratedgel film supported on a rigid support member for subjection toelectrophoretic or chromatographic procedures comprising a stiffresilient non-porous sheet of polymeric material having a thickness from3 to 10 mils and having a hydrophilic surface on which water spreads toa thin film, the bottom edge of said sheet being straight, flat, andfree from grooves and a handle connected to said sheet.